The Chemistry of Life

DP BioMs Wilson

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3.1 Chemical elements and water

• 4 elements most commonly found in living things (as we know them!)– Carbon– Hydrogen– Oxygen– Nitrogen

• What else do living things need? Why?

Water• Thermal properties– High specific heat (can absorb or release a lot of heat

without changing temp – temp stabilizer)– High heat of vaporization (cooling mechanism)

• Cohesive properties– Forms droplets– Surface tension (Jesus Christ lizard)– Moves as a column in plants– HSH and HHV

• Solvent properties– Glucose, amino acids, fibrinogen and hydrogencarbonate

ions (transport CO2) in blood

3.2 Carbs, lipids and proteins

• Carbohydrates – monosaccharides• Lipids – glycerol and fatty acids• Proteins (polypeptides) – amino acids• Nucleic acids – nucleotides

• Why are models of these molecules used? What do the molecules actually look like?

Functions of carbs:

Lipids

• Why are they important?– Insulation– Adipose cells hold more or less– Energy storage – think about this primitively– Phospholipid – what is that?

Hydrolysis and Condensation

• Hydrolysis: water “splitting” as part of reaction

• Figure 3.7

Condensation

• Condensation: water is a product• Figure 3.8

3.3 DNA Structure• Nucleotide: a phosphate group O=P, a deoxyribose sugar and a

nitrogenous base• 4 Nitrogenous bases

– Adenine– Thymine– Guanine– Cytosine

• Nucleotides are covalently bonded• Complementary pairs are hydrogen bonds (T and C are much

smaller than A and G)– C-----G– A-----T

• Check out heinemann.co.uk/hotlinks; ex code 4242P and click on Weblink 3.4

3.4 DNA Replication

• Hydrogen bonds undone so DNA can be copied– Helicase is an enzyme that does this

Formation of 2 complementary strands

• Free nucleotides also present – can bond to end of strand– These covalent bonds are catalyzed by DNA

polymerase

3.5 Transcription and Translation

Transcription

• Produces RNA using free nucleotides in nucleoplasm

• Only 1 strand of DNA is copied• mRNA is single stranded and shorter than DNA

(only 1 gene)• DNA has thymine and deoxyribose• RNA has uracil

• Figure 3.15 \/